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By G. van Aswegen

Large structures in mines (faults, dykes, pillars, abutments) fail when the load exceeds the strength. If the loading system stiffness (LSS, also referred to as the ‘local mine stiffness’) is lower than the stiffness of the structure the failure will be unstable. The greater the difference between these stiffnesses, the greater the energy release during unstable failure. A method has been formulated by which the LSS is established through cost-effective numerical modelling while insight into the structure stiffness (source stiffness - SS) is provided by apparent stiffness, a parameter based on the empirical relation between seismic moment and radiated seismic energy of small seismic events from the area/volume of interest. By plotting LSS vs SS a ‘stiffness diagram’ is constructed that is useful for seismic hazard ranking of different structures. A comparative back-analysis of the Dagbreek fault in Welkom, South Africa, (source of the 1990 Matjhabeng earthquake) and two other nearby faults confirm the applicability of the method. An extension of the method, where ‘hazard magnitude’ is used as a measure of the LSS, allows a ‘stiffness diagram’ to be constructed using seismic data only. Les larges structures dans les exploitations minières (failles, dikes, piliers, culées) s’écroulent lorsque la charge dépasse la résistance. Si la raideur du système de chargement (LSS, aussi appelé la « raideur de la mine locale ») est plus basse que la raideur de la structure, l’éboulement sera instable. Plus la différence est grande entre ces deux raideurs, plus l’énergie dégagée pendant l’éboulement instable est grande. Une méthode a été formulée selon laquelle le LSS est établi par modélisation numérique rentable, tandis que la raideur de la structure (SS – raideur de la source) est établie par la raideur apparente, un paramètre basé sur la relation empirique entre le moment sismique et l’énergie sismique radiée de petits moments sismiques dans l’aire/volume en question. On trace le « diagramme de raideur » en relevant les deux mesures (LSS et SS), ce qui est utile pour classer les risques sismiques de structures différentes. On vérifie l’applicabilité de la méthode en comparant la faille de Welkom, Afrique du Sud (foyer du séisme de Matjhabeng en 1990) avec deux autres failles proches. Une extension de cette méthode, dans laquelle on utilise la « magnitude du risque » comme mesure du LSS, permet de construire le « diagramme de raideur » avec des données sismiques seulement. Große Strukturen in den Gruben (Verwerfungen, Dämme, Pfeiler, Auflager) scheitern, wenn die Last die Stärke übersteigt. Wenn die Steifheit des Ladesystems (LSS, auch bezeichnet als `lokale Grubensteifheit’) niedriger ist als die Steifheit der Struktur wird der Bruch instabil. Je grösser der Unterschied zwischen diesen Steifheiten, desto grösser die Energiefreigabe während des instabilen Bruches. Es wurde eine Methode formuliert, durch die das LSS durch eine kosteneffektive numerisches Modell erstellt wird, während ein Einblick von der offensichtlichen Steifheit in die Struktursteifheit (Quellensteifheit - SS) gegeben ist, ein Parameter der auf der emipirischen Relation zwischen seismischem Moment und ausgestrahlter seismischer Energie von kleinen seismischen Ereignissen vom Interessens-/Volumenbereich basiert. Durch das Kartograpahieren der LSS in Bezug auf die SS wird ein `Steifheitsdiagramm ' konstruiert, welches für seismische Gefahrklassifizierung der unterschiedlichen Strukturen nützlich ist. Eine vergleichende Postanalyse der Dagbreek Verwerfung in Welkom, Südafrika, (Zentrum des Matjhabeng Erdbebens 1990) und in zwei anderen nahe gelegenen Verwerfungen bestätigen die Anwendbarkeit der Methode. Eine Verlängerung der Methode, in der die `Gefahrengröße' als Maß für das LSS verwendet wird, gestattet, daß ein `Steifheitsdiagramm' konstruiert wird, welches nur seismische Daten verwendet.

Jan 1, 2003

By R. G. B. Pickering

Over the last few years Lonmin Platinum and Sandvik have embarked on a unique partnership of collaboration through a systematic approach to developing equipment to mechanize and automate narrow reef platinum mining. After the initial design and manufacture of the equipment the key aspect is the integrating equipment, people and method into a mining system. Another key aspect of mechanization is the optimization of equipment utilization, and this philosophy has ensured continual evolvement of mining methods. This paper describes the trials and development that have resulted in the mining method described as Lonmin mechanized breast.

Jan 1, 2007

By J. Golamnejad

This paper attempts to model long-term production scheduling problems by chance constrained binary integer programming in a stochastic environment. This stochastic model is set up to account for ore block grade uncertainty. The probability distribution function of grade in each block is used as a stochastic input to the optimization model. This distribution function in each block should be determined using a Geostatistical Simulation approach. The deterministic equivalents of these chance constraints are then achieved, which are in the form of nonlinear in binary variables. A confidence level at which it is desired that the uncertain constraints holds, is specified in each scheduling period. Rather than the previous risk-based model, this formulation will yield schedules with a high chance of achieving planned production targets while maximizes the expectation of net present value and minimizing the variance function simultaneously. Using this method, the grade uncertainty is integrated explicitly into the optimization process.

Jan 1, 2006

By R. Chryst, R. Kus

In the Integrated IT Systems proposed by Przedsie? biorstwo Robót Geologiczno-Wiertniczych—Geological and Drilling Company (PRGW) a network connects a database with all of the departments of a mining division. A key element thereof is the common graphics environment—Micro Station supplied by the firm, Bentley. PRGW’s SoftMine software and GMSI’s CadsMine that are used to design and schedule mining operate in this environment. The digital form of the design project facilitates the verification of information and the integration of technical solutions with SAP R/3 type financial—accounting systems. The system has been successfully implemented in the Brown Coal Mine in Poland.

Jan 1, 2003

Since 2001, the Hybrid Stress Blast Model (HSBM) project members have developed a software suite to model the complete blasting process from non-ideal detonation to muck pile formation. To preserve the physics and improve solution time, the breakage engine uses a combination of analytical models and 2D axisym-metric finite differences to model near-field crushing, coupled to 3D discrete lattice fracturing and distinct element numerical methods to model throw and muck pile development. The model has been validated by comparison with laboratory and field tests in kimberlite. Multiple blasthole simulations are used to demonstrate how changes to blasting parameters can influence downstream efficiencies. Case studies of wall control blasting show that the presplit design must balance the two opposing effects of increased damage with increased charge and decreasing attenuation of the seismic waves with decreasing charge. Modelling of decoupled explosives needs further development. Reducing the charge towards the back of the trim blast results in a much more significant decrease in back damage than altering the timing. The model demonstrates how separation along the weaker planes in a jointed rock can coarsen the fragmentation, leading to inefficient beneficiation, and extends the damage to a distance of at least twice the burden behind from the blasthole, severely compromising the wall stability.

Jan 1, 2012

By I. Bhattacherya

Over the last three decades, the mining industry has been moving towards underground mechanized mining methods and the number of load haul dump (LHD) vehicles utilized has increased. The growth of mechanization and automation has benefited both workers and mining companies. However, due to the design constraints with LHD vehicles and the limitations of the operating environment, restrictions to operator visibility has contributed to a number of accidents, including fatal injuries. Past researchers have used the light filament technique to collect obscuration zones around mobile equipment and have produced 2D visibility charts (shadow diagrams) of this information. The light filament method involves manually collecting visibility data, which results in errors and is time consuming, requiring around three hours to complete. This research utilizes a MENSI GS100 laser scanner along with 3D modelling software (3Dipsos) to collect and process operator visibility profiles for underground mobile equipment. Results from this test work indicate that a laser scanner can be successfully used to rapidly collect this data and utilize this information for improved mobile equipment design from a visibility perspective. Nomenclature FERIC Forest Engineering Research Institute of Canada ISO International Organization for Standardization JACK Software for digital human modelling and ergonomics LHD Load haul dump vehicle LOS Line of sight MASHA Mines and Aggregates Safety and Health Association (based in Ontario, Canada) PVD Polar visibility diagram SAMMIE3D human modelling computer aided ergonomics design system WSIB Workplace Safety and Insurance Board

Jan 1, 2006

By P. J. Brereton-Stiles, C. J. Hockaday, I. J. Barker, M. S. Rennie

This paper reports on studies that have been done on the electrical conduction in silicon, ferro silicon, and charge chrome furnaces. A system has been developed that can distinguish between normal resistive conduction and arcing, and this was used to quantify in particular the relative amount of arcing that takes place in these furnaces. It was found that silicon and ferro silicon behave similarly and exhibit a relatively large amount of arcing. Charge chrome on the other hand exhibits considerably less arcing, and the extent of this arcing is highly correlated with the tapping of the furnace. The arcing measurements can also be used online in the control of the furnace, both for the electrodes and electrical circuit, and for the raw materials.

Jan 1, 2007

By R. Webster

"Daniel Krige’s influence on soil science, and on soil survey in particular, has been profound. From the 1920s onwards soil surveyors made their maps by classifying the soils and drawing boundaries between the classes they recognized. By the 1960s many influential pedologists were convinced that if one knew to which class of soil a site belonged then one would be able to predict the soil’s properties there. At the same time, engineers began to realize that prediction from such maps was essentially a statistical matter and to apply classical sampling theory. Such methods, though sound, proved inefficient because they failed to take account of the spatial dependence within the classes.Matters changed dramatically in the 1970s when soil scientists learned of the work of Daniel Krige and Georges Matheron’s theory of regionalized variables. Statistical pedologists (pedometricians) first linked R.A. Fisher’s analysis of variance to regionalized variables via spatial hierarchical designs to estimate spatial components of variance. They then applied the mainstream geostatistical methods of spatial analysis and kriging to map plant nutrients, trace elements, pollutants, salt, and agricultural pests in soil, which has led to advances in modern precision agriculture. They were among the first Earth scientists to use nonlinear statistical estimation for modelling variograms and to make the programmed algorithms publicly available. More recently, pedometricians have turned to likelihood methods, specifically residual maximum likelihood (REML), to combine fixed effects, such as trend and external variables, with spatially correlated variables in linear mixed models for spatial prediction. They have also explored non stationary variances with wavelets and by spectral tempering, although it is not clear how the results should be used for prediction. This paper illustrates the most significant advances, with results from research projects."

Jan 1, 2015

Control of flotation processes is mostly managed by plant operators, who assess the performance of the plant based on their own experience and other heuristic rules. These rules tend to be subjective or ill-defined, since most of them are concerned with the structure of the flotation froth, such as colour, bubble size and shape distributions, froth mobility and froth stability. These phenomena are very difficult to quantify objectively, and inexperience on the part of the operators, human error, etc., can lead to significant inefficiencies in plant operation. In this paper the development of a fuzzy system to support the control decisions of plant operators is described, which leads to significantly smoother control action and more stable plant operation than could be obtained with crisp sets of rules or manual control strategies. Keywords: flotation, fuzzy logic, image analysis, genetic algorithms, rule induction

Jan 1, 2000

By S. T. Johansen, C. Colomb, B. Ravary

Combustion and thermal NOx formation have been modelled using the Computational Fluid Dynamics (CFD) commercial code Fluent 6.1. The aim was to predict and give a better understanding of the combustion in electric arc furnaces for the production of ferro-silicon and silicon metal. Another important objective was to assess the impact of a number of operating parameters on the NOx formation. The CFD tools used are de-scribed with a special focus on models for species and turbulence transport. Sensitivity studies have been carried out to study the influence of several parameters: sub-models, process gas composition and distribution at the charge surface and influence of the presence of SiO. The main conclusions are: ?Using the combination of a realistic design, boundary conditions and models, the simulated NOx level is in quantitative agreement with measurements. The presence of water vapor is particularly important because of its influence on the specific heat of the mixture and resulting temperature. ?Release of significant amounts of SiO from the charge surface results in an important increase of NOx, even if we applied a simplified combustion model for SiO gas. However, because of lack of thermal and compositional data for blowing situations (when SiO flows directly from the arc cavity through open channels to the charge surface), no quantitative validation is possible. The way SiO is distributed (uniformly or as a jet) has a limited impact on the result in our computations.

Jan 1, 2007

By J. Kerr

The first stage of the development of a new modified 201-type low nickel austenitic stainless steel is described in this paper. The alloy is intended for use as a structural alloy, and so requires a yield strength >400MPa as well as acceptable weldability and toughness. The low nickel content will give a lower material cost in comparison to more conventional austenitic grades, and the processing route is required to be similar to that of Type 304 to keep the processing cost low. The base alloy was designed using empirical methods developed for stainless steel, and the properties of the base alloy were verified using a range of small-scale melts. The base alloy had a 0.2% proof strength of ~320-400MPa, and so it is planned to use V additions of ~0.15% to bring about precipitation strengthening in the hot rolled condition, so raising the alloy?s proof strength above the 400MPa minimum.

Jan 1, 2004

By D. Peatfield

The design and operation of coal preparation plants are governed by the inherent quality of the raw coal to be processed, market specifications and the saleable tonnage requirements. Topography influences the layout of the plant but does not affect the process design. The coal market comprises many sectors, each having specific requirements with respect to both size and quality. In turn, these have led to different levels of preparation and the development of specific types of coal preparation plant design. Developments in processing techniques and processing equipment have also influenced the design and now give the preparation engineer numerous permutations in process and equipment selection. This paper gives an overview of the coal industry in general and summarizes some of the developments in the design of plants and technical developments in the areas of dense medium processing, fine coal treatment and equipment design.

Jan 1, 2003

By G. J. van Tonder

The use of Molecular Recognition Technology (MRT), a highly selective separation technology using specifically designed ligands (such as macrocycles), has been demonstrated to be an effective treatment process for removal of several ions that are commonly found in many hydrometallurgical circuits as well as in environ-mental treatment operations. Ions removed by MRT include base, heavy and transition metals, precious metals, halides, and alkali/alkaline earths. A MRT pilot plant run was conducted at Zincor to demonstrate the cobalt/nickel purification of zinc electrolyte, and to recover saleable pure cobalt/nickel sulphate solution. The MRT process holds various advantages, which include the elimination of a catalyst such as arsenic trioxide, conventionally used in cobalt and nickel cementation. SuperLig® 138 can be used to remove cobalt and nickel from120?170 g/l Zn-solutions at pH 1?2. The Zincor MRT application demonstrated its capability of concentrating large volumes o copper barren impure solution at low cobalt and nickel concentration levels in the feed, to small solution volumes at high cobalt and nickel concentrations. Around 99.5% of the cobalt was removed from solution with cobalt impurity levels in feed varying between 10 mg/l and 26 mg/l.

Jan 1, 2002

By Reginald N. Boryor, Steven D. Woods

1.0 Introduction ?Low grade, high tonnage, open pit gold mine. ?Gold bearing Tarkwaian conglomerates. ?Reverse Circulation percussion drilling (25m X 25m grid). ?Composite 1m intervals, logged and split in the field to provide±2Kg samples. ?Samples used to build grade control block models using SURPAC. ?Approximately 100,000-130,000 meters drilled per year. ?RC samples are assayed using Rapid Cyanide Leach (RCL). ?Check assays are done using Fire Assay

Jan 1, 2005

By GA Harrison

The introduction of Extra Low Profile (XLP) mechanised equipment within Anglo Platinum is aligned with the overall New Mining Technologies strategy to focus on continuing modernization of our mining operations to achieve injury free sustainable production and cost effective mining technologies. The method allows for the introduction of a suite of XLP and Low Profile (LP) equipment in a narrow reef (1,2m) mining environment. For the first time it is now possible to achieve total trackless mechanisation at these stoping widths and XLP Breast mining has the potential to add more value when benchmarked with conventional mining and other mechanised methods. Various types of XLP equipment were tested at different sites within Anglo Platinum and this paper describes the XLP equipment evolution to-date. It concludes with recommendations on our future strategy regarding implementation and roll out of the XLP technology within Anglo Platinum.

Jan 1, 2008

By Y. Nakata, K. Nagata

Plasma is partially ionized gas composed of ions, electrons and activated elements at high temperature. Some flying ash from incinerated municipal waste is melted to become glass by a transfer-type arc plasma furnace. As the glass is ionic silicate, when an electric current passes through anode to cathode, ions in molten slag electrochemically react with electron in plasma at the surface of molten slag. In case of molten Na2O-SiO2, sodium ions in the molten slag carry electric current and SiO2are reduced to evaporate as SiO gas by electron in plasma. The cases of Ag+in NaNO3-KNO3molten salt and Fe2+in FeO-SiO2slag were examined. The amount of cathodic reaction is larger than that of anodic reaction and not apparently according to the Faraday?s law on the electrochemical reactions.

Jan 1, 2004

The current methodology to design stope support systems in South African gold and platinum mines is based upon the tributary area concept. The discontinuous nature of the hangingwall rock is not adequately addressed, and mechanisms leading to rock mass failures between adjacent support units are poorly understood. The work reported here aims to formulate a basis for quantifying support mechanisms and gain insights into the influence of rock discontinuities on stable hangingwall spans. Numerical models are used to qualitatively investigate the stress transfer from the support units to the discontinuous hangingwall. Stable hangingwall spans are quantified by considering two failure mechanisms, namely (i) beam buckling, and (ii) shear failure due to slip at the abutments. The output of the proposed design methodology is appropriate site specific support spacing, based on discontinuity spacing and orientation. The method is particularly suited to mines at intermediate and great depth, where typically the hangingwall is highly discontinuous due to face parallel mining induced fractures. Results of parametric studies show that with increasing in situ compressive hangingwall stress, beam thickness and friction angle, hangingwall stability is increased, leading to wider stable hangingwall spans between adjacent support units.

Jan 1, 2000

By M. Q. W. Jones

This paper summarizes important features of a compilation of thermal properties of stratified rocks from Witwatersrand gold mining areas. The database consists of more than 1000 thermal conductivity measurements, more than 700 density measurements, and nearly 100 heat capacity measurements. Most important rock types and stratigraphic units are well represented. Heat capacity does not differ significantly from one rock type to another, and density is relatively uniform although particular rock types are characterized by distinct average values. Different rock types also have distinct thermal conductivities, but this parameter varies by a factor of four to five. Primary factors controlling the thermal properties are mineral composition, degree of metamorphism, and porosity. In addition, the temperature dependence of thermal conductivity and heat capacity of quartzite may significantly decrease the thermal diffusivity of this rock at deep mining levels.

Jan 1, 2003

By Chad W. Brown

"A study of five commercially available solvent-extraction diluents in combination with three commercially available extractants under sub-Saharan African copper solvent-extraction conditions yielded intriguing results. A variety of physical and chemical property analyses showed that the diluents have some property differences, but overall the properties are similar and provide comparable solvent-extraction performance. Although each physical chemical property technique provides useful information, no individual test result suffices for prediction of diluent performance. Furthermore, a diluent should be evaluated within the conditions for which it is targeted to determine a true measure of performance. Overall, the diluents studied possess appropriate physicochemical properties for sub-Sahara Africa copper solvent-extraction conditions and can be utilized to achieve efficient, safe and reliable operations. INTRODUCTION Background Today, commercial SX diluents are available globally from a limited number of manufacturers. Production quality and consistency of these diluents have improved tremendously over the past 20 years. For example, diluent flash points have been increased incrementally to improve transport and handling while reducing fire hazards. In addition, properties have been successfully modified to minimize evaporative losses, ultimately reducing SX plant raw material costs. Diluent manufacturers have also focused on meeting performance requirements of SX plants, including eliminating components detrimental to SX operations, such as olefinic groups that can react with various species resulting in changing phase-disengagement properties over time, as well as ensuring that proper hydrocarbon components are present within diluent mixtures to maintain good reagent–metal complex solubility. These challenges have been met in the midst of ever-increasing stringent environmental regulations. Sub-Saharan Africa copper SX operations pose a unique set of conditions for diluents due to inherent ore compositions and the associated high reagent concentrations required for complete copper extraction. Chevron Phillips Chemical Company, LP has been manufacturing hydrocarbons and hydrocarbon-based diluents since the mid-80s, applying this experience to identify the physical properties considered crucial for proper performance in SX operations. This paper documents the findings of a study utilizing commercially available diluents in combination with extraction reagents commonly utilized in African SX operations to evaluate the relative performance of the diluents under sub-Saharan Africa copper SX conditions."

Jan 1, 2015

By Q. G. Reynolds

DC arc furnaces are widely used for steel scrap melting, and are increasingly being used for smelting applications as well. The electrical resistivity of slags varies widely, from highly conductive slags in ilmenite smelting, to highly resistive slags in applications such as cobalt recovery from non-ferrous slags, and nickel laterite smelting. Models have been developed to predict the electrical behaviour of the DC open plasma arc and the molten slag bath. These models allow the voltage and current ranges of furnace power supplies to be specified.

Jan 1, 2004